Horizontal semienclosed loop with conductive ground plane, having vertical whip extening from within loop enclosure



Jan. 17, 1967 P. TESSARI Ill 3,299,428

HORIZONTAL SEMIENCLOSED LOOP WITH CONDUCTIVE GROUND PLANE, HAVINGVERTICAL WHIP EXTENDING FROM WITHIN LOOP ENCLOSURE Filed Sept. 11, 19642 Sheets-Sheet FIG- I INVENTOR LAWRENCE R TESSARI m ATTORNEY Jan. 17,1967 L. P TESSARI in HORIZONTAL SEMIENCLOSED LOOP WITH CONDUGTIVE GROUNDPLANE, HAVING VERTICAL WHIP EXTENDING FROM WITHIN LOOP ENCLOSURE FiledSept. 11, 1964 2 Sheets-$heet 2 moi m m A R S O 5 T E m T a W R I. w 0 Nw M A W A L ZZmPZ Y .rzwmum B 80 m9 m 0? .m. 0 -m+ 02nd UnitedStatesPatent 3,299,428 HORIZONTAL SEMIENCLOSED LOOP WITH CON- DUCTIV E GROUNDPLANE, HAVING VERTICAL WHIP EXTENDING FROM WITHIN LOOP EN CLOSURELawi'ence P. Tessari III, 5871 Pine,

Taylor, Mich. 48764 Filed Sept. 11, 1964, Ser. No. 395,956 9 Claims.(Cl. 343-743) This invention relates to an antenna particularly adaptedto be used as both a transmitting and a receiving antenna for a mobileradio station operating in the general range of the higher frequencyamateur bands, that is, from approximately 2 to 150 megacycles. Itprovides an especially compact configuration and presents a very highradiation efficiency with respect to more conventional antennas whenemployed within these bands.

Mobile antennas are usually low efficiency radiating devices. A centerloaded whip, usually thought of as the most efficient mobile antenna,may be 30 db below a full sized reference dipole antenna in radiatingefiiciency at a frequency of about 4 megacycles. This low efiiciency ispartially due to the ground loss of the vehicle but a largepart of theinefficiency results from the necessity of employing antennas which aremuch smaller than required for a maximum efficiency and a consequentnecessity to employ loading devices in the form of lumped constant coilsand capacitors in order to electrically tune the antennas to thestations frequency. These lumped constants are negligibly efficient asradiators and constitute a major portion of the inefficiency of themobile antennas. When lumped constants are necessarily employed it isdesirable, when possible, toemploy capacitors rather than inductorsbecause a theoretically perfect capacitor is much more easily achievedin practice than a theoretically perfect inductance.

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I antenna is necessary to provide an exact tuning a capaci- Anotherproblem associated with the mobile antennas configuration which may beemployed for both transmitting and receiving on mobile equipment whereinlittle, if any, lumped loading constants must be employed, in whichthese lumped loading constants may be capacitors, and in which a DC.short to ground may be employed without reducing theantennas'transmission efficiency. The antenna is characterized by anextremely high radiating efiiciency relative to its dimensions, thisefficiency appreciably exceeding other known mobile antennaconfigurations.

In a preferred embodiment of the invention, which will be subsequentlydisclosed in detail, the antenna takes the form of a wire ring having anopening along its length, disposed parallel to and slightly raised abovesome relatively large metallic surface of the automobile, such as theroof or the trunk lid, which acts as a ground plane. One of the ends ofthe ring connects to a radially extending connecting section whichterminates at the center of the ring in a right angle bend, therebyforming a stub end which extends along the axis of the ring in adirection away from the plane of the ring. The other end of the ring isconnected directly to the metallic surface thereby forming a DC. shortto ground for the elimination of precipitation static during receiving.An input coaxial line from the transmitter receiver connects to the twoopen ends of the ring. In the event that some loading of this tor may beinserted between the right angle bend which joins the radial section tothe axially extending section and the other side of the capacitor may beconnected to the ground surface.

This antenna may be viewed as a directional discontinuity ring radiatorcombined with a whip antenna. The directional discontinuity ringradiator (DDRR) is described in CO Magazine, June 1964, pages 2831. Itbasically comprises an open ended loop disposed parallel to, and above,a metallic ground plane. This antenna exhibits a normally inductiveimpedance and it therefore neatly matches the normally capacitiveimpedance exhibited by a Whip antenna. By connecting them in the mannerspecified their capacitive and inductive impedances balance out so as toprovide a primarily resistive impedance and a resultant high radiatingefficiency. The relative positions of the antenna members in theinventive configuration are such as to provide reinforcement rather thaninterference between the radiated waves sections, adding to the highradiation eificiency.

The exact dimensions and configuration of the inventive antenna aredependent upon the maximum dimensions imposed by the physicalconfiguration of its mounting and the frequency on which it is used. Ithas been found that the developed length of the antenna should equal thefull quarter wave length. This is, of course, not possible at the lowerfrequencies and the capacitor, preferably variable, must be used as atuning element.

It is therefore seen to be a primary object of the present invention toprovide a mobile antenna which consists of a circular open-endedradiating element mounted in ahorizontal plane a short distance above anelectrical ground plane and having one of its ends connected to agenerally radial segment which is, in turn, connected to an axiallyextending whip section.

Other objects, advantages, and applications of the present inventionwill be made apparent by the following detailed description of thepreferred embodiment of the invention. The description makes referenceto the accompanying drawing, in which: FIGURE 1 is a perspective view ofan antenna formed in accordance with the present invention: and FIGURE 2is a graph radiating power versus frequency for the antenna of thepreferred embodiment, 2. standard dipole antenna, a whip antenna, and aDDRR antenna.

Referring to the drawing, the disclosed embodiment of the presentinvention is preferably used on an automobile or other mobile vehicleand is mounted in proximity to a generally horizontal sheet metalsection of that vehicle, indicated at 10, which may constitute a sectionof the roof or the trunk lid thereof. Supported above the surface 10,which acts as an electrical ground plane, is a ring 12 formed of wire,preferably having a circular configuration. The ring 12 is not quiteclosed. The ring 12 is supported above the ground plane 10 on a numberof insulators 14 which are spaced at regular intervals about the ring.The two open ends each lead into right angle connecting sections. Oneconnecting section 14 extends radially inward to the center of theantenna. The radially extending section 15 connects toand is formedintegrally with a whip section 18 which joins the section 16 at a rightangle bend at the center of the ring 12 and extends axially away fromthe plane of the ring. The extreme end of the whip section 18 may beprovided with a ball for decorative purposes and for minimizing coronadischarge.

The other end of the ring 12 terminates in a short connecting section 22which extends perpendicularly from the plane of the ring and makescontact With the metallic ground plane 10. The end of the section 20 maybe soldered or otherwise electrically connected to the metallic plane. I

The antenna makes connection with a transmitter and receiver through alead-in line 24, which preferably takes the form of a coaxial cable. Oneof the wires of the cable 26 is connected to the ring 12 immediatelyadjacent the joinder with the connecting section 20 and the other cablelead 28 is connected to the ground plane.

The developed length of the antenna may be made equal to one quarter ofthe wave length of the operating frequency. When this is not possible,the antenna must be tuned to the operating frequency by a capacitor 30which connects electrically to the right angle bend between theconnecting section 15 and the whip section 18 and also to the metallicground plane 10. The capacitor 30 may also serve as a support for thewhip section. The capacitor 30 may be fixed or variable in order toadjust to various operating frequencies.

In contrast to a conventional DDRR antenna, wherein the developed lengthof the ring must be at least a quarter wave length in order to obtainnatural resonance, in the present invention the developed length of theentire antenna, including the ring 12, the connecting section 16, andthe Whip 18, may be included in determining the resonant length. Thus,the present antenna may have an appreciably smaller diameter than anequivalent DDRR antenna, and as has been noted, its overall radiationefficiency is higher. The ratio between the diameter of the ring 12 andthe length of the whip antenna whip section 18 is dependent upon thephysical configuration. Normally the diameter 12 will be made equal toor slightly smaller than the length of the whip. This re sults in acompact and stable configuration.

It should be recognized that the configuration of various embodiments ofthe present invention need not be identical with that of the preferredembodiment: that is, the ring 12 need not be absolutely circular,although noncircular configurations do not result in increasedefiiciency: the whip section 18 need not be exactly in center and itwould be possible to use a conducting section other than wire for theconnecting section 15. Other variations may be made within the spirit ofthe following claims.

FIGURE 2 is a graph of the radiation efiiciencies of a number ofantennas, including an embodiment of the present invention, plotted as afunction of frequency. On the chart the vertical parameter is radiatedpower ratios taken with respect to a full sized dipole. For purposes ofpreparing this graph a DDRR antenna, a whip antenna, and an embodimentto the present invention, each tuned to 28 megacycles, were employed. Itshould be noted that the present antenna was less efiicient than theDDRR antenna but much more efficient than the whip antenna belowapproximately 4 megacycles. Between 4 megacycles and approximately 8megacycles the present antenna was more efficient than either a DDRR ora whip. Above approximately 8 megacycles the whip became slightly moreefficient than the present antenna although the present antenna was muchmore efiicient than the DDRR. The antenna of the present invention thusexhibited a relatively good gain over a wider band width than either theDDRR or a whip antenna.

The present antenna may of course be employed in fixed as well as mobilesituations.

Having thus described my invention, I claim:

1. An antenna, comprising: a planar metal section generally disposed inthe horizontal plane: an elongated conductive section disposed abovesaid metallic plane, bent into a semienclosed configuration lying in thehorizontal plane: a straight elongated whip section extending in thevertical direction from a point within said semienclosed configurationaway from said planar section: and a conductive connecting sectionjoining one end of said semienclosed configuration to the end of saidwhip section which is within said semienclosed section.

2. An antenna, comprising: a metallic ground plane disposed in thehorizontal plane: an elongated conductive and within the enclosure ofsuch section in a direction away from the ground plane: and a conductiveconnecting section joining one end of said semienclosed section to theend of the whip within the plane of said section.

3. An antenna operative to be connected to a transmitter-receiver bymeans of a two wire lead-in cable, comprising: a metallic ground plane:an elongated conductive section bent into a configuration which isclosed but for a relatively short gap between the ends thereof disposedparallel to and separated from said ground plane: an elongated whipsection extending in a direction perpendicular to said ground plane froma point within the plane of said semienclosed section and within theenclosure thereof in a direction away from the ground plane: a firstconnecting section joining one end of said semienclosed section to theend of the whip within the plane of said semienclosed section: a secondconnecting section joining the other end of said semienclosed section tosaid ground plane, said second connecting section extendingperpendicular to the ground plane: and connections between one end ofsaid semienclosed section, the ground plane, and the two wires of saidlead-in.

4. The structure of claim 3 wherein the developed length of thesemienclosed section, the first connecting section, and the whip isapproximately equal to one quarter wave length of the operatingfrequency of the antenna.

5. An antenna operative to be connected to a transmitter-receiver by atwo connector lead-in, comprising: a metallic ground plane: an elongatedconductive section bent into a semienclosed configuration with its twoends separated from one another by a distance which is small compared tothe developed length of said section, said section being disposedparallel to and separated from said ground plane: a whip sectionextending perpendicularly to said ground plane from a point within theplane and the enclosure of said semienclosed section in a direction awayfrom the ground plane: a first conductive section connecting a point onthe semienclosed section adjacent to one of the ends thereof to the endof said whip which is in the plane of said semienclosed section: asecond conductive section connecting a point adjacent to the other endof said semienclosed section to the ground plane, said second conductivesection extending perpendicularly to the ground plane: a lumpedimpedance connected between the ground plane and a termination of thewhip within the plane of the semienclosed section: and connectionsbetween the two ends of the lead-in and'two points on the semienclosedsection.

6. The structure of the last claim 5 wherein the lumped impedance is acapacitor.

7. The structure of claim 5 wherein the lumped impedance is a variablecapacitor.

8. An antenna operative to be connected to a transmitter-receiver by atwo conductor cable, comprising: a metallic ground plane: an elongatedconductor section bent into a semicircular configuration with its twoends slightly separated from one another: a plurality of insulatorssupporting said semicircular section parallel to the ground plane andseparated from it: an elongated whip section extending from a pointwithin the plane of said semicircular section perpendicular to suchplane away from the ground plane: a first conductive connecting sectionjoining one end of said semicircular section to the end of the whipwithin the plane of said semicircular secton: a second conductiveconnecting section joining the other end of said semicircular section tothe ground plane: and connections between the two wires of the lead-into points on the circular section.

9. An antenna operative to be used in connection with atransmitter-receiver to which it is connected by a two conductor cable,and operative to be disposed in relation to a metallic ground planewhich may form a section of a supporting vehicle, comprising: aconductive section bent in a semicircular configuration: a plurality ofinsulators supporting said semicircular section above and parallel tosaid ground plane: an elongated Whip section extending from a pointwithin said semicircular section in a direction perpendicular to andaway from said ground plane: a first conductive section connecting oneend of said semicircular section to the end of the whip which isdisposed within the plane enclosed by said semicircular section: asecond conductive connecting section adjoining the other end of saidcircular section to the ground plane: a capacitor connected between theground plane and the end of the whip which is within the plane of saidsemicircular section: and connections between the ends of 3,151,3289/1964 Boyer 343744 3,235,871 2/1966 Smith et al. 343-872 FOREIGNPATENTS 938,921 2/ 1956 Germany.

OTHER REFERENCES Boyer, Hula-Hoop Antennas, ElectronicsJanuary 11, 1963.Pages 44-46 relied on.

15 HERMAN KARL SAALBACH, Primary Examiner.

R. F. HUNT, Assistant Examiner.

1. AN ANTENNA, COMPRISING: A PLANAR METAL SECTION GENERALLY DISPOSED INTHE HORIZONTAL PLANE: AN ELONGATED CONDUCTIVE SECTION DISPOSED ABOVESAID METALLIC PLANE, BENT INTO A SEMIENCLOSED CONFIGURATION LYING IN THEHORIZONTAL PLANE: A STRAIGHT ELONGATED WHIP SECTION EXTENDING IN THEVERTICAL DIRECTION FROM A POINT WITHIN SAID SEMIENCLOSED CONFIGURATIONAWAY FROM SAID PLANAR SECTION: AND A CONDUCTIVE CONNECTING SECTIONJOINING ONE END OF SAID SEMIENCLOSED CONFIGURATION TO THE END OF SAIDWHIP SECTION WHICH IS WITHIN SAID SEMIENCLOSED SECTION.